1. Field of the Invention
The present invention relates to an image drying device for physically drying a toner image formed on a surface of a photoconductor in a wet type image forming apparatus for a wet electrophotographic type multi-color printer, copy machine or the like which performs liquid development.
2. Description of the Related Art
In a copy machine, a printer or the like of wet electrophotographic recording system which performs liquid development, a liquid carrier for charging toner is contained in a developing fluid as a primary component in order to selectively develop toner particles dispersed in the developing fluid. Therefore, it is required a process for absorbing only liquid component and drying solid component up to about 95 to 97% for forming a film in order to sufficiently dry the image and forming a film of a multi-color image in an order of several to several tens microns before transferring the toner image onto a printing paper using a pressure and a heat.
One of technologies for performing the process has been disclosed in Japanese Unexamined Patent Publication No. Heisei 11-231743. Disclosed in the above-identified Japanese Unexamined Patent Publication No. Heisei 11-231743 has a construction, in which a squeezing roller and a pack-up roller are arranged in opposition to each other at a location downstream of a developing roller performing liquid development with respect to a belt photoconductor for clamping the belt photoconductor developed by the developing roller by the squeezing roller and the back-up roller for removing the ink deposited on the portion other than latent image of the belt photoconductor by the squeezing roller, in conjunction therewith drying the developed image by the squeezing roller for forming the film, and cleaning the squeezing roller by means of a blade.
However, the method of drying (forming a film) by means of the squeezing roller encounters a difficulty in providing sufficiently large peripheral length in the squeezing roller and in obtaining sufficient area for absorbing, dispersing and evaporating a developing solvent or the like other than toner. Therefore, in the squeezing roller, it is repeated operation to again contact with the belt conductor before drying of the surface per se or evaporation of the developing solvent to make adhesive force of the surface of the squeezing roller excessively and non-uniformly high due to impurity contained in the developing solvent having viscosity to peel off (picking) the toner image on the belt photoconductor by the squeezing roller which is originally designed for removing the developing solvent or the like other than the toner. As a result, temporary image degradation, such as white out and so forth can be caused on the printing medium. Furthermore, the toner particle peeled off the surface of the developing roller may deposit on the surface of the squeezing roller to lower absorption perform in the portion where the toner is deposited. As a result, the toner image on the photoconductor becomes too wet to be a cause of color shade or the like due to failure in transfer when large number of copies are printed. Therefore, difficulty is encountered in constantly maintain a predetermined image quality. Also, if the peripheral length of the squeezing roller is short, degradation of function becomes quick to shorten the life.
It is an object of the present invention to provide an image drying device which can provide sufficient area for absorbing, dispersing and evaporating a developing solvent or the like other than toner, improve efficiency of drying by absorbing the developing solvent or the like other than toner from the surface of the photoconductor after formation of the toner image, eliminate occurrence of peeling off (picking) of the toner image to peel off the toner image from the photoconductor and thus maintain a predetermined image quality for a long period.
In order to accomplish the above-mentioned object, the present invention employs a belt in place of the conventional squeezing roller to circulate the belt with contacting with a surface of a photoconductor after formation of a toner image to absorb the developing solvent or the like other than toner from the surface of the photoconductor, and to heat the belt for promoting evaporation.
According to the first aspect of the present invention, an image drying device of a wet type image forming apparatus comprising:
a drying belt circulating in a conduction contacting with a surface of a photoconductor after formation of a toner image and absorbing a developing solvent or the like other than toner from the surface of the photoconductor; and
a cleaning roller incorporating a heater and rotating with contacting with the drying belt.
According to the second aspect of the present invention, an image drying device for a wet type image forming apparatus comprising:
a nip roller;
a heating roller incorporating a heater therein; and
a drying belt wound between the nip roller and the heating roller for circulation, being heated by the heating roller and being urged to contact with a surface of a photoconductor after forming a toner image for absorbing a developing solvent or the like other than toner from the surface of the photoconductor.
According to the third aspect of the present invention, an image drying device for a wet type image forming apparatus comprising:
a nip roller;
a heating roller incorporating a heater therein;
a drying belt wound between the nip roller and the heating roller for circulation, being heated by the heating roller and being urged to contact with a surface of a photoconductor after forming a toner image for absorbing a developing solvent or the like other than toner from the surface of the photoconductor; and
a cleaning roller incorporating a heater and rotating with contacting with the drying belt.
The first to third aspect of the present invention further comprises cleaning roller moving mechanism for moving the cleaning roller between a contacting position where the cleaning roller contact with the drying belt and a retracted position where the cleaning roller is placed away from the drying belt in order to maintain the performance of the drying belt for long period.
The cleaning roller moving mechanism may place the cleaning roller at the contacting position while the wet type image forming apparatus is in printing operation and at the retracted position otherwise.
The cleaning roller may be preliminarily heated to a predetermined temperature by means of a heater incorporated therein before being moved from the retracted position to the contacting position.
The cleaning roller may be heated by the heater incorporated therein at the retracted position for regeneration whenever number of printing of the wet type image forming apparatus reaches a preliminarily set number.
With the foregoing constructions, particularly in the second and third aspect of the invention of the image drying device, the nip roller, the heating roller and the drying belt may be combined as a drying unit, and the image drying device further comprises a drying unit moving mechanism for moving the drying unit so that the drying belt is displaced between a contacting position where it contacts with the surface of the photoconductor and a retracted position placed away from the surface of photoconductor.
In case of the third aspect of the invention, the cleaning roller moving mechanism is cooperated with the drying unit moving mechanism.
The drying unit moving mechanism may drive the drying unit to move to the contacting position to contact the drying belt with the surface of the photoconductor while the wet type image forming apparatus is in printing state, and to the retracted position otherwise.
The heating roller may be heated at a predetermined temperature by a heater incorporated therein before the drying unit is moved from the retracted position to the contacting position.
The drying unit may circulate the drying belt by own driving system independently of the photoconductor.
The drying belt is formed by forming an elastomer layer of a material absorbing a developing solvent or the like on a surface of a base material of polyethylene terephthalate resin.